1. Field of the Invention
The present invention relates to a projector that projects light onto a screen to display images.
2. Description of the Related Art
As an apparatus for displaying images having arbitrary sizes, a projector is available that adjusts light emitted by a light source, based on video signals received from a personal computer, and uses the adjusted light to project images onto a white screen. The adjustment of the light by the projector is performed in the manner described, for example, in JP-UM-A-6-055131. That is, white light emitted by a light source, a lamp, is split, using a separation mirror, into beams of the three primary colors, red, green and blue, and the three beams are fed into a light shutter that, in accordance with video signals, controls how much of each of the individual received beams is permitted to pass through. The three beams are then synthesized, using a synthesis mirror, to obtain a single light beam that is projected through a lens and onto a screen, forming an image thereon.
For this conventional projector, since the luminance of an image displayed on the screen depends on screen gain, the luminance must be adjusted each time the screen is changed. Therefore, according to the projector disclosed in JP-UM-A-6-055131, while irradiation of the screen is being performed, based on a reference signal, a luminance detection sensor, provided on the front face of the projector, receives light reflected by the screen and detects the luminance level of the reflected light. When the detected luminance level is higher than a reference value, the luminance is automatically changed so as to reduce the contrast of a video signal. Whereas when the detected luminance level is lower than the reference value, the luminance is automatically changed so as to increase the contrast of the video signal.
Further, for the conventional projector, the focal length of the lens must be adjusted to project a focused image on the screen. Therefore, according to a projector disclosed in JP-A-2001-343703, while irradiation of a screen is being performed, a light flux reflected from the screen is projected through a lens and a beam splitter to a light-receiving device, and based on a signal output by the light-receiving device, the focal point of the lens is adjusted automatically.